Ga2O3 nanorod-based extended-gate field-effect transistors for pH sensing

Abstract In this study, the pH-sensing characteristics of gallium oxide (Ga2O3) nanorods based on an extended-gate field-effect transistor were grown on the ITO/glass via chemical bath deposition. Ga2O3 nanorods were observed using scanning electron microscopy, X-ray diffraction, energy-dispersive spectrometry, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and Raman spectrum instruments. The experimental results showed that the α-Ga2O3 nanorods had several crystalline orientations ([1 0 4], [1 1 0], [0 2 4], [1 1 6]) after being annealed at 400–600 °C for 1 h. The FTIR and Raman spectrum measurements confirmed the existence of Ga−O and Ga−OH bending modes. As observed by the TEM, the nanorods had a good crystal quality and atomic lattice arrangement. In addition, the Ga2O3/ITO pH sensor possessed high pH sensitivity (51.59–64.29 mV/pH), good linearity (98.5%–99.8%), and long-term stability (drift, 2.75 mV/h; pH = 7). Overall, the α-Ga2O3 could be used as a low-cost FET-based manufacturing sensor for pH or biosensors.